Pipes puzzle

Discussion in 'DIY Marinizing' started by pengreg, Aug 28, 2005.

  1. pengreg
    Joined: Feb 2005
    Posts: 52
    Likes: 2, Points: 0, Legacy Rep: 40
    Location: South Africa

    pengreg Junior Member

    I am restoring an old yacht and trying to figure out the engine cooling piping which had been partially removed, this is what I have:

    40Hp marinised Massey Fergusen (standard) motor with usual waterpump, one outlet is piped (approx 30mm Dia) to a (wet?) exhaust mainfold

    Hydraulic gearbox with external oil cooler with (approx 10mm) fittings both ends

    Two shallow rectangular vessels either side of the keel with two through hull fittings (approx 30mm diam) each which I am assuming are keel coolers

    An un-insulated stainless pipe exhaust with a tall S bend and a 10mm tee fitting just before the manifold

    One perforated plate intake (sea chest?) with a 10mm fitting

    A small reservoir (app 5 L) with a 10mm fitting

    This is what I think it all means:

    Hot water from the motor is pumped through the exhaust manifold and then splits to the top of each of the coolers respectively. Cold water from the bottom of each of the coolers joins and is then fed back to the motor, with a small reducing tee somewhere for the line to the reservoir

    As a separate system, raw water from the intake is led through the gearbox cooler and then into the top of the exhaust - as far as I can see there is no pump on this line?

    Please could anyone comment or point me to a drawing
  2. Jango
    Joined: Aug 2005
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    Location: Mid Atlantic

    Jango Senior Enthusiast

    Pipes puzzel

    I am not familar with the Engine cooling but would like to comment about the Trans.

    I believe the Transmission oil is cooled by passing the oil thru an external cooler in the raw sea water circuit. Transmission oil is pumped with an internal Transmission oil pump thru the cooler and returned to the pump.

    Water lines are usually larger than 10mm.

    Hope this helps, Jango
  3. Poida
    Joined: Apr 2006
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    Location: Australia

    Poida Senior Member

    I thought a wet exhaust was where the water is piped directly to the inside of the manifold and is blown out of the exhaust??

    I have just made the same query myself as the engine in the boat appears to be hosed up wrong, possibly by a previous owner.

    I assume from your description your engine cools from a heat exchanger and I would think you would have one pump outlet going into the engine, out of the head into the exhaust manifold jacket and then to the heat exchanger.

    The other pump outlet would go to the trans and into the other heat ex. inlet.

    I am guessing here but is it possible since you don't have a pump on the raw water side that the water is sucked through by connecting it to the exhaust via the connection you mentioned in a ventury type pumping.

    Maybe an idea to post a pic of your engine so those really in the know can help you.


  4. pengreg
    Joined: Feb 2005
    Posts: 52
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    Location: South Africa

    pengreg Junior Member

    pipes, pipes

    Hi Poida! I had forgotten the post completely. Yes thank you I have found a good description in Nigel Calder's Boatowners electrical and mechanical manual. I was correct in my assumption except that there is a pump to the exhaust system. I believe that the the exhaust supply should be just after the manifold, because of the danger of water backing into the engine.

    Kind regards
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